Three-dimensional semiconductor device

1. A three-dimensional semiconductor device, comprising: a semiconductor substrate; a lower insulation layer covering a top surface of the semiconductor substrate; a semiconductor layer contacting a top surface of the lower insulation layer, the semiconductor layer including first, second, third, and fourth well regions doped with first conductivity impurities, the first and second well regions that are adjacent to each other in a first direction, the first and third well regions that are adjacent to each other in a second direction crossing the first direction, and the second and fourth well regions that are adjacent to each other in the second direction; and first, second, third, and fourth cell array structures disposed on the first, second, third, and fourth well regions of the semiconductor layer, respectively, wherein the first and the second directions are parallel to the top surface of the semiconductor substrate, wherein each of the first, second, third, and fourth cell array structures comprise: a stack structure including a plurality of stacked electrodes stacked in a vertical direction on a top surface of the semiconductor layer; and a plurality of vertical structures penetrating the stack structure and connected to a corresponding well region of the first, second, third, and fourth well regions, wherein the semiconductor layer further includes a separation impurity region between and in contact with the first, second, third, and fourth well regions, the separation impurity region comprising a pair of impurity regions doped with second conductivity impurities different from the first conductivity impurities, wherein the semiconductor layer further includes a dummy impurity region between the pair of impurity regions and doped with first conductivity impurities, wherein the pair of impurity regions doped with the second conductivity impurities comprise: a first region continuously extending along the second direction between the first and second well regions and between the third and fourth well regions; and a second region continuously extending along the first direction between the first and third well regions and between the second and fourth well regions, wherein entire bottom surfaces of the pair of impurity regions are at the same level as entire bottom surfaces of the first, second, third, and fourth well regions, wherein the pair of impurity regions and the dummy impurity region have the same doped depth in the vertical direction, and wherein the semiconductor layer includes a plurality of PN junctions formed by the dummy impurity region and the pair of impurity regions.

2. The three-dimensional semiconductor device of claim 1, wherein the semiconductor layer consists of a single layer that extends in the first and second directions.

3. The three-dimensional semiconductor device of claim 1, wherein the semiconductor layer includes a plurality of PN junctions formed between the first, second, third, and fourth well regions and the separation impurity region.

4. The three-dimensional semiconductor device of claim 1, wherein the separation impurity region has a width less than a width of one of the first, second, third, and fourth well regions, in the first direction.

5. The three-dimensional semiconductor device of claim 1, wherein the semiconductor layer has an opening that penetrates a portion of the separation impurity region.

6. The three-dimensional semiconductor device of claim 1, wherein the separation impurity region has substantially the same depth as those of the first, second, third, and fourth well regions.

7. A three-dimensional semiconductor device, comprising: a semiconductor substrate; a lower insulation layer covering a top surface of the semiconductor substrate; a semiconductor layer contacting a top surface of the lower insulation layer, the semiconductor layer including first and second well regions, first and second separation impurity regions spaced apart from each other and disposed between the first and second well regions and a dummy impurity region disposed between the first and second separation impurity regions, the first and second well regions doped with first conductivity impurities and the first and second separation impurity regions doped with second conductivity impurities, and the dummy impurity region doped with first conductivity impurities different from the second conductivity impurities; and first and second cell array structures disposed on the first and second well regions of the semiconductor layer, respectively, wherein each of the first and second cell array structures comprises a stack structure including a plurality of electrodes stacked in a vertical direction on a top surface of the semiconductor layer, wherein each of the first and second separation impurity regions includes a first portion extending along a first direction and a second portion extending along a second direction between the first and second well regions and intersecting the first portion, wherein the semiconductor layer consists of a single layer that extends in the first and second directions, wherein the semiconductor layer includes at least two PN junctions formed by the dummy impurity region and the first and second separation impurity regions, and wherein portions of the first and second separation impurity regions doped with the second conductivity impurities contact the first and second well regions, wherein the semiconductor layer has a first thickness in the vertical direction, wherein each of the first and second separation impurity regions has a first depth in the vertical direction, the first depth being the same as the first thickness, wherein the dummy impurity region has a second depth in the vertical direction, the second depth being the same as the first thickness, wherein the first and the second directions are parallel to a top surface of the semiconductor substrate, and wherein a first side surface of the dummy impurity region contacts a side surface of the first separation impurity region and a second side surface of the dummy impurity region contacts a side surface of the second separation impurity region.

8. The three-dimensional semiconductor device of claim 7, wherein each of the first and second separation impurity regions has a width less than a width of one of the first and second well regions, in the first direction.

9. The three-dimensional semiconductor device of claim 7, further comprising: a peripheral logic structure including a semiconductor substrate, peripheral logic circuits on the semiconductor substrate, and a lower buried insulation layer covering the peripheral logic circuits, wherein the semiconductor layer is disposed on a top surface of the lower buried insulation layer.

10. The three-dimensional semiconductor device of claim 9, further comprising: an upper buried insulation layer on the semiconductor layer and covering the stack structure, wherein the semiconductor layer comprises an opening between the first and second well regions adjacent to each other in one direction and exposing the lower buried insulation layer, the opening of the semiconductor layer being filled with the upper buried insulation layer.

11. The three-dimensional semiconductor device of claim 7, wherein each of the first and second well regions has a third depth in the vertical direction, the third depth being the same as the first thickness.

12. A three-dimensional semiconductor device, comprising: a peripheral logic structure including a peripheral logic circuit integrated on a semiconductor substrate; a semiconductor layer on the peripheral logic structure and including first and second well regions and a separation impurity region between the first and second well regions, the first and second well regions doped with first conductivity impurities and the separation impurity region doped with second conductivity impurities different from the first conductivity impurities; and a cell array structure provided on each of the first and second well regions of the semiconductor layer, wherein the cell array structure comprises: a stack structure including a plurality of stacked electrodes stacked in a vertical direction on a top surface of the semiconductor layer; and a plurality of vertical structures penetrating the stack structure and connected to one of the first and second well regions, wherein the separation impurity region surrounds each of the first and second well regions, when viewed in a plan view, wherein the semiconductor layer consists of a single layer, wherein the separation impurity region comprises a pair of impurity regions doped with the second conductivity impurities, wherein side surfaces of the separation impurity region contact side surfaces of the first and second well regions, wherein top and bottom surfaces of the separation impurity region are coplanar with respective top and bottom surfaces of the semiconductor layer, wherein top and bottom surfaces of the first and second well regions are coplanar with the respective top and bottom surfaces of the semiconductor layer, and wherein the separation impurity region vertically overlaps a portion of the peripheral logic circuit.

13. The three-dimensional semiconductor device of claim 12, wherein the peripheral logic structure further includes a lower buried insulation layer covering the peripheral logic circuit, and wherein the semiconductor layer comprises an opening between the first and second well regions adjacent to each other in one direction and exposing the lower buried insulation layer.

14. The three-dimensional semiconductor device of claim 12, wherein the peripheral logic structure further includes a lower buried insulation layer covering the peripheral logic circuit, and wherein the first and second well regions and the separation impurity region are in contact with a top surface of the lower buried insulation layer.

15. The three-dimensional semiconductor device of claim 12, wherein the pair of impurity regions doped with the second conductivity impurities include: first portions extending in a first direction and spaced apart from each other in a second direction crossing the first direction; and second portions extending parallel to the second direction and spaced apart from each other in the first direction.

16. The three-dimensional semiconductor device of claim 12, wherein the separation impurity region has substantially the same depth as those of the first and second well regions.

17. The three-dimensional semiconductor device of claim 12, wherein the semiconductor layer includes a first PN junction formed between the first well region and the separation impurity region and a second PN junction formed between the second well region and the separation impurity region.

18. The three-dimensional semiconductor device of claim 17, further comprising: an upper buried insulation layer on the semiconductor layer and covering the stack structure, wherein the semiconductor layer comprises an opening between the first and second well regions and exposing the lower buried insulation layer.

19. The three-dimensional semiconductor device of claim 18, wherein the opening of the semiconductor layer is filled with the upper buried insulation layer.